Recent Advances in Anisotropic Conductive Films … · Dept. of Materials Science & Engineering ......
Transcript of Recent Advances in Anisotropic Conductive Films … · Dept. of Materials Science & Engineering ......
-
Nano Packaging & Interconnect Lab.
Prof. Kyung W. PaikKorea Advanced Institute of Sci. and Tech.(KAIST)
Dept. of Materials Science & EngineeringNano Packaging & Interconnect Lab.
IEEE CPMT Santa Clara Chapter9/9/2015
San Jose, CA USA
Recent Advances in Anisotropic Conductive Films (ACFs)
Technology for Wearable Electronics
-
1. Wearable Market trends
Wearable device in movies Now, start wearble device war
-
Nano Packaging and Interconnect Lab.
Divergence to wearable device
Wearable devices perform subsidiary functions of smart phone by using wireless network.
* Reference : 2014 (KT )
Convergence to Smart Phone
Apple, iwatch
Nokia, Finger Fit
Nike, Fuel Band
Google, google glass
Hub
Tatoo, Pennsylvania univ.
Smartshoes
Smart cloths Smart ring
3
Wearable electronics trends
-
4IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
wearable devices for each body parts
Miniaturization Light weight Flexibility Reliability High performance
Trends in wearable electronic devicesRef)
Google glass : https://www.google.com/glass/start/Smart contact lens : http://googleblog.blogspot.kr/2014/01/introducing-our-smart-contact-lens.html
Galaxy gear : http://www.samsung.com/us/mobile/wearable-tech/SM-V7000ZKAXARMC10 sensor : http://www.mc10inc.com/
-
5IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
It was partially flexible. Interconnection part was not bendable. Package itself has to be flexible.
Trends in wearable electronic devices
PCBRigid package
Nike-google fuel band
Flexible package is necessaryfor wearable electronic devices
Source) Nike
-
1. Wearable Market trends
What is current wearable applications?
-
1-1. Fitness and Wellness - Bracelets
Flexible Interconnection
Bracelets Teardown (Jawbone)
Rigid Substrate locate the right location to avoid bending reliability issuesThe Interconnection is connected by FOB between Rigid and FPC.
-
1-2. Informative Device - Smartwatch
1. Samsung KMF5X0005M AP (DRAM package, 1 GHz dual-core CPU )
2. Maxim Integrated MAX77836 (likely micro-USB interface controller and
battery)3. STMicroelectronics 32F401B
32 bit ARM Cortex MCU4. 0225E8 E225B45. BCD Semiconductor Y831 audio code6. InvenSense MP65M
6-axis gyroscope / acceleromete
1)
2)3)
4)6)
5)
Tear-down of galaxy gear 2
-
1-2. Informative Device Smart Glass
Google Glass
- Competitor : Samsung Gear Glass Launch (2014, 2Q)
Item Component RemarkS/W Android 4.0.4Display 640360
displaynHD (640 x 360) Display
Active Device
AP Texas Instruments OMAP 4430 SoC1.2Ghz Dual(ARMv7) Special Order
DRAM 1 GB Mobile DRAM (Elpida)
Flash 16GB storage (12 GB available)
Sensor MEMS : 3 axis gyroscope 3 axis accelerometer3 axis magnetometer (compass)
WirelessCommunication
Bluetooth, Wi-FiBone conduction transducer
Camera 5-megapixel capable of 720p video recording
Charger Included Micro USB cable and chargerBattery Single-cell Li-Polymer Battery at the end
flexprint PCB(2.1Wh)
Add Substructure to the glasses
-
1-2. Informative Device Google Glass Google Glass Teardown
Main Board(Flash / DRAM /BT / Wifi)
Sub BoardFOB Interconnection
Touch InterfaceConnectors
Rigid PCB, FPC, solder SMT, Connector based interconnection
-
1-3. Healthcare & Medical Wearable sensors Advanced Wearable Sensors
* Source : ETRI ( IT, 2013.07)
Fabric Wire interconnection(IZM 2013)
Mechanical Contact
SOC(Silicon on Clothes) sensor, (Hoi-Jun Yoo, KAIST)
Interconnection is challenging!
-
1-4. Industrial and Military
4. Industrial and military
- Application : Hand worn terminals, Augmented reality heat-sets etc.
Hand worn terminals (WT41N0) Motorola
Head Up Guidance System (HGS)(Flight Dynamics Inc.)
-
Flexible/Wearable Electronics 4 Core HW Technologies
1. Flexible LSI Devices 2. Flexible Batteries3. Flexible Displays4. Flexible Packages & Assembly
Flexible Interconnect Connector-based : Not good for flexibility Solder-based : Not good for flexibility ACF-based
Flexible IC Packages ACF COF/CIF Flexible Connectors ACF FOB /FOF
-
1. Flexible LSI Device
ACS Nano, 7(5), 4545, 2013
14/16
-
Nano Packaging and Interconnect Lab
Samsungs Curved Smartphones using OLED on Polymer films
LG Displays Flexible Display
LGs G Flex Smarphones
2. Flexible Display - OLED
-
3. Flexible Battery
-
17IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Anisotropic Conductive Films (ACFs) for flexible electronic packaging General 3 electrical connection methods
1) Pressure interconnection
Source) Samsung Galaxy S4
No flexibility
2) Solder interconnectionSource) Samsung
Fatigue solder crack
3) Adhesive interconnection: ACF (Anisotropic conductive film)
Flexibility
FPC substrate
ACF
ACF
ACF
FPC substrate
FPC substrate
Polymer resin
Conductive polymer ball
-
CONFICURATION
Peel Strength;5g/inch
Peel Strength;25g/inch
Thermal Curable Resin
ConductiveParticle
Cover Film (38)
Antistatic WhiteReleasable Film
(50)
Particle can be exchangeaccording to uses
Ni(500)
Au(500)Polymer Bead (5)
ACF configuration
-
Nano Packaging & Interconnect Lab.
Anisotropic Conductive Films (ACFs)
Thermosetting epoxy resin film Conductive particles+ ACF =
Chip or substrate 1
Substrate 2
Heat
Chip or substrate 1
Substrate 2
Pressure
ACFACF
Chip-On-Glass (COG)Chip-On-Flex (COF)Flex-On-Glass (FOG)
Chip-On-Flex (COF) Chip-On-Board Flex-On-Board (FOB)
Applications of ACFs assemblyThermal curing
-
20IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Issues on ACF flexible package structure for wearable electronics
1. Flexible IC Package geometry design2. Optimization of ACF materials
ACF Polymer Resin & Conductive balls3. Fine pitch ACF interconnect
Nanofiber ACFs (>20 um pitch)4. Current carrying capability
Solder ball ACFs + Ultrasonic bonding5. Reliability
-
21IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Issues on ACF flexible package structure for wearable electronics
1. Flexible IC Package geometry design2. Optimization of ACF materials
ACF Polymer Resin & Conductive balls3. Fine pitch ACF interconnect
Nanofiber ACFs (>20 um pitch)4. Current carrying capability
Solder ball ACFs + Ultrasonic bonding5. Reliability
-
22IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Thin chip
FPC substrate
Thermosetting resin(mechanical adhesion)
Conductive polymer ball(electrical conduction)
Heat & pressure
Anisotropic Conductive Film
Chip-on-Flex package using ACFs is suitable for flexible package structure.
Anisotropic Conductive Films (ACFs) for flexible chip electronic packaging
ACF
-
COF/CIF Packages interconnected using ACFs
Nano Packaging and Interconnect Lab.23
Ultra-thin Silicon chip(30um~40um)
Ultra-thin Silicon chip(30um~40um)
Flexible Substrate(Polyimide Film)
Flexible Substrate(Polyimide Film)
Flexible Interconnectusing ACF
Flexible Interconnectusing ACF
Thermosetting resin(Mechanical adhesion)Thermosetting resin
(Mechanical adhesion)
Conductive particles(Electrical conduction)Conductive particles
(Electrical conduction)
Temperature, Pressure, Time
Conductivity, Insulation, Adhesion
Materials & interconnection type
-
24IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
COF(Chip-on-Flex)/CIF(Chip-in-Flex) package using ACFs
Electrode
bump
Chip
FPCB
ACF resin
Cover adhesive film
Cover Polyimide film
Polymer ball
Chip-in-flex package
1. Flexible IC Package geometry design:
-
25IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Cover polyimide film
Cover adhesive film
Location of the Neutral axis & the Maximum Tensile Stress depending on Package Structure & Package Geometry
Chip
FPCBcompression
tension
Neutral axis
Chip-on-Flex
Neutral axis : axis with no strain or no stress
Chip-in-Flex
y
-
26IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
COF CIF60
80
100
120
140
Max
imum
tens
ion
stre
ss o
n ch
ip (M
Pa)
The location of the Maximum tensile stress on the chip surface depending on COF/CIF packages
Maximum tensile stress
@ concave bending radius : 5mm
Cover adhesive film (30 m)
Chip
Substrate
Cover polyimide film
Chip
Substratecompression
tension
NA
NA
compression
tension
y
x
COF CIF
ymaxymax
ACF : Reference ACF
Concave Bending
-
27IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Issues on ACF flexible package structure for wearable electronics
1. Flexible IC Package geometry design2. Optimization of ACF materials
ACF Polymer Resin & Conductive balls3. Fine pitch ACF interconnect
Nanofiber ACFs (>20 um pitch)4. Current carrying capability
Solder ball ACFs + Ultrasonic bonding5. Reliability
-
28IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
2. Optimization of ACF materials : ACF polymer resin property on the flexibility of CIF PKG
Cover adhesive film (30 m)
Chip
FPCB
Cover polyimide film
CIF packages ACF resin property
ACF
ACF Modulus
Low modulus ACF 0.9 GPaReference ACF 1.57 GPa
High modulus ACF 1.82 GPa
Evaluation of CIF package bending reliability depending on
ACF polymer resin property
Polymer ball
Electrode
bump
Resin
-
29IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
0 2000 4000 6000 8000 10000 12000
0
50
100
150
200
250
300
350Da
isy-
chai
n re
sist
ance
(Ohm
) at
radi
us 7
.3 m
m
Cycles
L/M ACF Ref ACF H/M ACF
Effects of ACF resin properties on the flexibility of CIF PKG under dynamic bending test
1,500 cycles
In-situ dynamic bending test 160k cycles (@ R7.3 mm)
6,000 cycles9,000 cycles
As modulus of ACF increased, dynamic bending life increased.
ACF Low modulus ACFReference
ACFHigh modulus
ACF
Modulus 0.9 GPa 1.57 GPa 1.82 GPa
-
30IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Issues on ACF flexible package structure for wearable electronics
1. Flexible IC Package geometry design2. Optimization of ACF materials
ACF Polymer Resin & Conductive balls3. Fine pitch ACF interconnect
Nanofiber ACFs (>20 um pitch)4. Current carrying capability
Solder ball ACFs + Ultrasonic bonding5. Reliability
-
Nano Packaging & Interconnect Lab.
Samsung unveils its entire UHD TV lineup at CES 2014, leading with a 110-inch monster.
UHD(Ultra High Definition) & QHD(Quad High Definition) LCD panel requires ultra fine pitch I/O interconnection!UHD: 4K Technology
-
Nano Packaging & Interconnect Lab.
r Unstable electrical performances on fine pitches
Short circuit: agglomerated CPs electrical conduction in X-axes
Open circuit / high resistance: Non-captured or small # of CPs in Z-axis higher joint resistance poor reliability
Short circuit Open circuit
Finer pitch
Issues for Fine Pitch Interconnection Using ACFs
How can we suppress conductive particle movements?
Increasing viscosity?Gulbi at Korea
-
Nano Packaging & Interconnect Lab.
Suppressing CP movement No short circuit & open circuit
v Korea patent :10-1115686 (issued):10-1146351 (issued):10-1160971 (issued):10-2011-0022041
Why Nanofiber ACFs?
v Japan patent pending:2011-072488:2012-532008
v China patent pending:201110111458.0
Nanofiber ACF
CP incorporated nanofiber (CPIN)
Adhesive resin
X-Insulation Z-ConductionChip
Substrate
v PCT patent pending:PCT/KR2010/006623
v USA patent pending:13/075,147
Ref) Kyoung-Lim Suk, Chang-Kyu Chung and Kyung-Wook Paik, 61st ECTC, Florida, USA, May 31-June 3, 2011.
Conductive particles incorporated nanofiber
(CPIN)
-
Nano Packaging & Interconnect Lab.
Nanofiber ACFs Fabrication
A: Syringe, B: Needle, C: High voltage power supply, D: Nano-fibers, E: Collector units
Polymer solutionr Nanofiber formation by electro-spinning
NCF lamination on Conductive particle coupled nanofiber
-
Nano Packaging & Interconnect Lab.
8 particles/bump (1024 m2)
97% 77%
26.8% 26.8%
v Nanofiber ACF suppressed the particle movement compared to the conventional ACF during resin flow.
r Conductive particle movement during the bonding process
Conventional ACFNanofiber ACF
Initial ACF state
CPIN capturing Nanofiber melting & resin curing
Particle Capture Rate of Nanofiber ACFs
Pre bonding Main bonding
-
Nano Packaging & Interconnect Lab.
r X-axis insulation resistance r Short circuit rate at 20 m pitch
v Nanofiber ACF successfully suppressed the conducive particle movement resulting in zero short circuit rate at 20 m pitch.
ACF Nanofiber ACFConventional ACFs
Nanofiber ACFs
ACF Nanofiber ACFConventional ACFs
Nanofiber ACFs
CPs
Short Circuit Rate of Nanofiber ACFs
-
37IEEE 65th ECTC San Diego, CA, USA May 26 29, 2015Add Authors Name Here
Issues on ACF flexible package structure for wearable electronics
1. Flexible IC Package geometry design2. Optimization of ACF materials
ACF Polymer Resin & Conductive balls3. Fine pitch ACF interconnect
Nanofiber ACFs (>20 um pitch)4. Current carrying capability
Solder ball ACFs + Ultrasonic bonding5. Reliability
-
Nano Packaging & Interconnect Lab.
Recent issues in mobile device packages - Modulization
Source : Nokia
Current trends in mobile devices
1. High performance
2. Multi-functionalization
3. Miniaturization
Conventional Socket-type connectors
Advantages Fine pitch capability Reduced package size Process effectiveness
FOB(Flex-on-Board) & FOF (Flex) assemblyusing ACFs
Disadvantages Large volume & height Large pitch size400 um pitch
ACFFPCB
PCB
-
Nano Packaging and Interconnect Lab.
Conductive particleConductive particleACF
FPCB Mechanical adhesion
Electrical conduction
Thermosetting resinThermosetting resin
Electrode PCB
Anisotropic Conductive Films (ACFs) for FOB assembly
ACF FOBs in wearable devices
Thermo-compression
(T/C)
Source :Samsung electronicsGoogle company
Galaxy Gear
Google glass
- Large volume- Large pitch size
ACFRigidPCB
FlexiblePCB
- Reduced package size- Fine pitch capability
ACF FOB Advantages
Source: Nokia
May 26 May 29, 2015
-
Nano Packaging and Interconnect Lab.
Solder ACFs for high current handling capacity
ACF ACF
ElectrodesOrganic rigid board
Electrodes
Flexible substrateFlexible substrate
Organic rigid board
Conventional ACF Solder ACF + U/S
Solderparticle
Electrode
Electrode
Adhesive
Physical point contact of metal particles Limitations in electrical properties and reliability
Metallurgical bonding of solder particles
Higher current carrying capability
Improved reliability
Patent pending
Heat generationUp to 300 oC
Metalparticle
Adhesive
Electrode
Electrode
Ni ball Metal coated polymer ball Solder ball
-
Solder particles in ACFs : Solder Oxide Layer problems Ultrasonic Bonding
5um
Solder
Electrode
Electrode
Thermo-compression (TC) bonding
TC
ACF
PCB
Flexible PCB
Ultrasonic bonding
Nano Packaging and Interconnect Lab.Nano Packaging and Interconnect Lab.
Partial solder wettingby remained solder oxide layer
ACF
PCB
Flexible PCB
0Solder
Electrode
Wetted solder
Solderoxidelayer
Ultrasonic
Electrode
Wettedsolder
Excellent solder wettingby broken solder oxide layer
May 26 May 29, 2015
-
Nano Packaging & Interconnect Lab.
ACFs bonding Thermocompression(T/C) vs. Ultrasonic(U/S)
Chip or substrate 1
Substrate 2ACFHeat conduction
T/C ACFs bondingHeating tool
U/S ACFs bonding
Chip or substrate 1
Substrate 2
U/S horn
Local heat generation
Heating tool (250~350)ACF temperature (180)
Thermal conduction slow Thermal damages High Energy waste
U/S horn (R.T.) ACF temperature(> 250)
Fast (1/2 ~ 1/3 bonding times) No thermal damages Energy saving (No heating, 1/10)
Heat
Patented
-
Nano Packaging & Interconnect Lab.
Vision systemU/S part
Stage
U/S controllerMain controller
The 1st Commercial U/S ACF bonding machine MPB-U110 : 1 head, 1 stage, manual alignment
-
Nano Packaging & Interconnect Lab.
Advantages of U/S vs. T/C ACF bonding1.Reduced Assembly Times & Cost
Faster ACFs bonding times of U/S method Epoxy ACFs: 3 ~ 5 sec. vs. 7 ~ 15 sec. Acrylic ACFs: 1 ~ 3 sec vs. 5 ~ 7 sec.
2.No thermal damage on boards T/C bonding induces thermal damages to boards No thermal damages by U/S
No bonding tool heating Very effective on FOB (organic PCBs) such as PET or PC based
Touch Screen Panel (TSP) and flexible display (polymer OLED) assembly
3.Eco-Processing Significant energy saving
Very little U/S loading cycle No idling energy loss digital control
-
Nano Packaging and Interconnect Lab.
Conventional T/C : 160 oC 2MPa 6 secU/S : 225 oC 2MPa 5 secSolder ACF joints - Contact resistance
0
2
4
6
8
10
12
Cont
act r
esis
tanc
e (m
Ohm
)Contact resistances
Conv.ACF
20umsolderACF
45umsolderACF
The solder ACF joints showed 30% lower contact resistances than that of the conv. Ni ACF joints due to solder alloy bonding of solder particles.
-
Nano Packaging and Interconnect Lab.
Current carrying capability
Conventional T/C : 160 oC 2MPa 6 secU/S : 225 oC 2MPa 5 sec
Solder ACF joints - Current carrying capability
0.0 0.5 1.0 1.50.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Curr
ent (
A)
Bias (V)
45um solder ACF 20um solder ACF Conv. ACF
Conv. ACF
20um solder ACF 45um solder ACF >30%
The PCB line burns before ACF joint failure. At least 4X increase of power handling capability
(1 Watt 4 Watt)
Joint failureat 1.6 A
Joint failureat 2.66 A
PCB line burningat 3.0 A
Line width : 160 umLine thickness : 18 um
60%
-
Nano Packaging and Interconnect Lab.
0 20 40 60 80 100 120 140 160 180 2000
20
40
60
80
100
0 hrs 5 hrs 10 hrs
Contact resistance (mOhm)
Cum
ulat
ive
dist
ribut
ion
(%)
0 20 40 60 80 100 120 140 160 180 2000
20
40
60
80
100
0 hrs 5 hrs 10 hrs
Contact resistance (mOhm)
Cum
ulat
ive
dist
ribut
ion
(%)
0 20 40 60 80 100 120 140 160 180 2000
20
40
60
80
100
0 hrs 5 hrs 10 hrs
Contact resistance (mOhm)
Cum
ulat
ive
dist
ribut
ion
(%)
Rapid degradation of physical point contacts
Unbiased autoclave test results
Conventional Ni ACF 20 um solder ACF
Stable resistances Stable resistances
(121 oC, 2 atm, 100%RH, 48 hrs)
Conventional T/C : 160 oC 2MPa 6 secU/S : 225 oC 2MPa 5 sec
Solder ACF joints - Reliability
45 um solder ACF
Early failures
-
Nano Packaging and Interconnect Lab.
Summary
For flexible packaging & interconnect for wearable electronics applications,
1. ACF COF & CIF packages provide excellent chip flexibility by optimizing PKG structure design and ACF materials and processing.
2. And ACF FOB & FOF & Fabric assembly using solder ACFs combined with Ultrasonic bonding offer 30 lower joint resistance, >4X power handling capability, high reliability, and great flexibility for wearable electronics applications!